Lens coating to reduce external fogging of scope lenses

ABSTRACT

A coated lens for use in a riflescope, telescope, spotting scope, binoculars, or the like is provided. The coating on the lens comprises two layers, an anti-reflective layer adjacent the lens and a hydrophobic layer disposed on the anti-reflective layer. The hydrophobic layer preferably includes an organosilane compound. Advantageously, the coating does not significantly reduce light transmission through the lens.

RELATED APPLICATIONS

[0001] This application is a divisional of application Ser. No.10/291,452, filed Nov. 8, 2002 which was a continuation of applicationSer. No. 09/961,750, filed Sep. 24, 2001 which was acontinuation-in-part of application, Ser. No. 09/451,787, filed Dec. 1,1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present application is directed toward a coating for anexterior surface of a telescope lens, especially a riflescope, aspotting scope, or a binocular to reduce the likelihood of fogging ordistortion due to the collection of moisture on the lens withoutsignificantly reducing light transmission through the lens in thevisible range. More particularly, the present invention is directedtoward such coatings that are durable. Still more particularly, suchcoatings may include two layers with the first layer being ananti-reflective (AR) coating which has either a single layer or multiplelayers such that light transmission in the visible range is notsignificantly reduced and the second coating is a durable hydrophobiccoating over the AR coating. Still more particularly, the presentinvention provides a coating which is not easily scratched or worn awayundergoing standard durability and abrasion testing.

[0004] 2. Description of the Prior Art

[0005] Scopes used by sportsmen, military and the like, have improvedsignificantly over the years. However, much of this improvement is loston cold days or rainy days due to collection of moisture or fogging onthe lens which then significantly distorts the image. For example, ahunter on a cold day will often bring the gun to his face to aim througha scope at a target, and in doing so often breathes on the scope's lens.The hunter's breath then fogs the lens. On days when it is raining ordrizzling, the moisture from the rain can likewise collect on the lensand distort the image. While the interior face of the lens can beprotected against the elements by placement of a moisture free gaswithin the interior of the scope, the exterior face of the lens isinvariably exposed to the elements and incurs the fogging and moisturecollection noted above.

[0006] Various treatments have been previously utilized that applyhydrophobic materials to various articles, such as sunglasses andautomobile windshields, to produce beading of water droplets/or thequick sloughing of moisture, so that the moisture is not retained andspread unevenly on the article due to surface tension so as to producedistortion. However, such treatments reduce the transmissions of lightthrough the article. Typically this reduction in transmission occurseven if the treatment is essentially clear or see through, since theindex of refraction of the treatment is different in comparison to theindex of refraction of the article causing some amount of reflection tooccur. The light that is reflected is then not seen by the viewer whichreduces the quality of the image. In articles such as windshields andsunglasses, the amount of reduction in light transmission is notcritical, and therefore, a loss of a small amount is not considered tobe extremely important.

[0007] However, in riflescopes and other telescopic devices, it isextremely important to maintain light transmission in the visible rangenear 100 percent of incident light in order to ensure that the bestpossible quality image is seen through the scope. Conventionaltreatments for rendering articles hydrophobic reduce the transmission oflight in certain visible ranges sufficiently to make use of suchtreatments unacceptable.

[0008] Anti-reflective treatments are used on various materials todecrease reflection and increase transmission of light, especially incertain wavelengths. Anti-reflective treatments have been previouslyused in the prior art for various types of devices, including lenses.Anti-reflective treatments have been especially used where lenses withmultiple components are joined together in a side-by-side (or layered)relationship. However, hydrophobic polymers that naturally reducetransmission of light do not adhere to most of the components ofanti-reflective treatments that increase transmission of light. Even ifthe hydrophobic polymer will adhere to an anti-reflective, it has beenfound through testing that the hydrophobic polymer can often easily beremoved by rubbing or just general wear over time.

[0009] Consequently, it is desirable to provide an overall coating foran exterior face of a riflescope lens or the like, which includes anexternally located hydrophobic polymer that transmits light in thevisible range and causes quick beading and sloughing of moisture fromthe lens. Furthermore, the hydrophobic polymer requires ananti-reflective component that is designed to allow almost one hundredpercent of visible light at selected wavelengths to be transmittedthrough the lens and the hydrophobic polymer. Still furthermore, it isimportant that the hydrophobic coating be strongly adhered to the lensand not easily removed by rubbing or wear over time. Additionally, whatis needed is a hydrophobic lens coating having a certain hardness ordurability which provides a certain degree of protection for the lens orany AR layers located on the lens such that the coating is not easilyscratched. In this respect, it is desirable that the hydrophobic lenscoating be of sufficient hardness and durability to undergo conventionaltesting without significant damage to the hydrophobic coating, any ARcoating, or the lens itself.

SUMMARY OF THE INVENTION

[0010] The present invention overcomes the problems inherent in theprior art and provides a distinct advance in the state of the art. Acoating is provided for lenses to render the exterior face or surface ofthe lens hydrophobic to reduce the likelihood of fogging and to reducethe likelihood of distortion of images passing through the lens bycollection of water thereon. The coating comprises two layers; the firstlayer being an anti-reflective treatment and the second layer being alight transmitting hydrophobic polymer treatment.

[0011] The anti-reflective layer includes multiple sublayers, thematerial of construction of which and the thickness of which are chosento provide the best transmission of selected wavelengths through thelens in conjunction with the particular hydrophobic polymer utilized.The number of sublayers in the anti-reflective layer may vary inaccordance with design techniques and typically range from three toseven in number. Preferably, the anti-reflective layer has foursublayers.

[0012] The outer layer of the anti-reflective layer, that is the layeropposite the lens and adjacent the hydrophobic layer is constructed ofsilicon dioxide. The anti-reflective layer is applied in ways well knownin the art. However, in order to make the hydrophobic polymer layer wearresistant, it is best to heat the anti-reflective layer above ambienttemperature. Preferably the anti-reflective layer is heated to atemperature in the range of 250-300° centigrade provided that the lensis constructed of glass that can withstand such temperatures. Inalternative methods, the anti-reflective coating is applied to a lensusing vapor deposition or sputtering.

[0013] Alternatively, the outer layer of the anti-reflective layer canbe formed of any conventional AR coating and it is desirable to selecteach AR layer based upon the desired AR characteristics of the finalproduct. Of course, this is also true for single-layer AR coatings.

[0014] While the anti-reflective layers may be constructed of numeroustypes of materials, one particular preferred embodiment includes 70nanometers of aluminum oxide (Al₂O₃), 70 nanometers of ZrO₃, 225nanometers of MgF₂ and 140 nanometers of SiO₂ where it is desired thatthe wavelength of visible light at 550 nanometers be most clearly andcompletely transmitted through the lens.

[0015] One preferred method of applying this coating (including both anAR layer and a hydrophobic coating) generally includes the steps ofapplying an AR coating to a lens under vacuum in a first chamber andthen having the hydrophobic coating applied to the AR-coated lensapplied using vapor deposition in a second vacuum chamber. Anotherpreferred method applies the AR coating to a lens using sputtering withthe final layer being sputtered on being the hydrophobic coating. Thisprocess is especially adapted for AR coatings which do not incorporatesilicon dioxide as the layer occurring just beneath the hydrophobiccoating as any AR layer could be used.

[0016] In one aspect of the present invention, a coating is applied to alens which has an AR coating thereon. In other words, the lens has atleast two layers on one of the surfaces. The first layer is the AR layerand the second layer is the hydrophobic coating. The AR layer can be ofany AR material and may be comprised of several layers of different ARmaterials. On top of this AR layer, the hydrophobic coating is applied.This hydrophobic coating is preferably a coating which does notsignificantly affect light transmission and which provides a durableouter layer which is not easily scratched or marred. The hydrophobiccoating should also adhere to the underlying AR layer such that it isnot easily removed. The hydrophobic coating is preferably anorganosilane compound. Preferred organosilane compounds applied tolenses will retain at least 95% of its hydrophobic characteristics afterundergoing a standard eraser test. Still more preferably, thehydrophobic coating will retain at least 97% (and even more preferablyat least 98.5%) of its hydrophobic characteristics after undergoing astandard eraser test. Most preferably, the hydrophobic coating willretain at least 99.5% of its hydrophobic characteristics afterundergoing a standard eraser test. One method of testing the hydrophobiccharacteristics would include measuring the contact angle of a waterdrop both before and after the eraser test. Furthermore, when undergoinga standard adhesive tape test, the coating should retain less than 5% ofthe applied stain with the remaining 95% being removed by the adhesivetape. Still more preferably, the hydrophobic coating will permit removalof at least 97% (and even more preferably at least 98.5%) of the stainundergoing a standard adhesive tape test. Most preferably, thehydrophobic coating will permit removal of at least 99.5% of the appliedstain after undergoing a standard adhesive tape test. With respect tolight transmission, the hydrophobic coating should have little to noeffect and riflescopes containing a plurality of lenses therein shouldexhibit less than a 5% loss of light through the lenses. Preferably, anyone lens having an AR coating on each side of the lens and a hydrophobiccoating applied to at least one of the sides of the lens should have atleast 99% light transmission therethrough. A particularly preferredorganosilane compound is PERMASEAL (Nanofilms, Inc., Valley View, Ohio).

[0017] Therefore the principle objects of the present invention are: toprovide a telescope lens having an external face that is treated with acoating to resist accumulation of water on the lens to reduce thelikelihood of fogging and to reduce the likelihood of distortion due tocollection of moisture acting under surface tension thereon; to providesuch a lens having a high percentage of transmission of light in thevisible range; to provide such a lens wherein the coating comprises aanti-reflective layer and a hydrophobic polymer layer on the surface ofthe lens; to provide such a lens wherein the anti-reflective layer has asublayer of silicon dioxide that is adjacent to the hydrophobic layer;to provide such a lens wherein the anti-reflective layer is heatedduring manufacturing and while on the lens to a temperature aboveambient temperature and preferably to a temperature in the range of250-300° centigrade; to provide such a lens that has very close to 100%transmission of light over a very wide spectrum of visible light; toprovide a lens having an AR layer and a hydrophobic coating on top ofthe AR layer wherein the hydrophobic coating provides increaseddurability while having little to no effect on light transmission; andto provide such a lens which is relatively easy to construct,inexpensive to produce and especially well suited for the intended usagethereof.

[0018] Other objects and advantages of this invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention.

[0019] The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a perspective view of a hunter utilizing a rifle with ariflescope having a lens treated in accordance with the presentinvention;

[0021]FIG. 2 is a fragmentary side elevational view of the riflescope,with portions broken away to show placement of the lens therein;

[0022]FIG. 3 is a fragmentary and very highly enlarged cross-sectionalview of the lens and various coating layers on the surface of the lens;

[0023]FIG. 4 is a graphical representation of light transmission throughthe lens at various wavelengths; and

[0024]FIG. 5 is a graph illustrating the light transmission through ariflescope in accordance with the present invention in comparison toother riflescopes.

DETAILED DESCRIPTION OF THE INVENTION

[0025] As required, detailed embodiments of the present invention aredisclosed herein; however, it is to be understood that the disclosedembodiments are merely exemplary of the invention, which may be embodiedin various forms. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as abasis for the claims and as a representative basis for teaching oneskilled in the art to variously employ the present invention invirtually any appropriately detailed structure.

[0026] The reference numeral 1 generally indicates a lens in accordancewith the present invention mounted in a riflescope 4 that is in turnmounted on a rifle 5 that is illustrated as being aimed by a user 6 inFIG. 1.

[0027] The scope 4 is of a type conventionally used on rifles bysportsmen and the like, although it is foreseen that many types oftelescope systems such as binoculars, spotting scopes and the like maybe treated with the present invention. The scope 4 may include multipleinternal lenses and related internal components which are quiteconventional and are not illustrated in detail or highly describedherein. The invention is specifically directed to the lens 1 which hasan external face 10 that is exposed to the ambient environment,especially rain and the breath of the user.

[0028] The lens face 10 is positioned during use in front of an eye 11of the user 6 and in doing so, the user 6 often exhales a breath 12 thatis supersaturated with moisture from the lungs of the user 6. The user'sbreath 12, as well as falling or driven rain or mist, engages the lensexternal face 10. Under typical circumstances, the breath 12 uponstriking the lens face 10 or rain or mist on the lens face 10 will causethe lens 1 to fog or the images seen therethrough to become distorteddue to surface tension acting on the moisture on the lens 1.

[0029] Consequently, in accordance with the present invention, the lensface 10 is covered with a coating 15 that reduces surface tension andcauses beading of moisture, thereby significantly reducing thelikelihood of image distortion through the lens 1 due to moisturecollecting thereon. The coating 15 is very thin in thickness and doesnot show as a separate layer in FIG. 2 for this reason. The coating 15is best illustrated in FIG. 3 which is highly enlarged fragmentary viewof a portion of the lens 1 and coating 15. The entire thickness of thecoating 15 will typically be less than 1000 nanometers (nm). In order tonot affect light transmission, the coating must be very thin as comparedto the wavelength of light of interest. For example for a wavelength of550 nm, the coating must be much thinner than 550 nm. Preferably, thecoating is less than 50 nm thick. The coating 15 includes ananti-reflective layer 18 and a hydrophobic layer 19.

[0030] The anti-reflective layer 18 is best specifically designed orengineered for the particular lens 1 and hydrophobic layer 19 utilizedtherewith. Design of anti-reflective layers, such as layer 18, issomewhat both an art and a science. Conventionally there have been manydifferent types of anti-reflective layers that have been developed forvarious lenses and for various purposes.

[0031] The typical anti-reflective layers include multiple sub-layerswhich are each made of materials which are different from adjacentsub-layers and which are typically deposited in thicknesses wherein thethickness of each sublayer is related to an even whole number divisionof the wavelength of light that is most preferred to be transmittedthrough the lens 1.

[0032] For example, light that has a wavelength of 550 nm and isapproximately in the middle of the visible range is typically consideredto be an important wavelength to be transmitted through the lens 1.Therefore, the sub-layers of the anti-reflective layer 18 may be chosento be deposited in proportion to the 550 nm wavelength. As an example, acommon coating that is three sub-layers in thickness is often depositedin layers that are ¼, ½ and ¼ of the length of the wave of thewavelength or 140 nm, 220 nm, and 140 nm in thickness. The artassociated with production of anti-reflective coatings and how todeposit such coatings on articles is well known to those having ordinarykills in the art. In particular, the art of designing and depositinganti-reflective layers on objects can be found in such references as theHandbook of Optics by McGraw Hill, 2^(nd) Ed., in Chapter 42, Dealingwith Optical Properties of Films and Coatings, Design of OpticalInterference Coatings by McGraw Hill Book Company in Chapter 4 onAnti-Reflection Coatings, as well as in issued U.S. patents to Kimura etal., U.S. Pat. No. 4,726,654, Akatuska et al., U.S. Pat. No. 4,784,467and Tani, U.S. Pat. No. 4,387,960, which are all included here inreference.

[0033] Anti-reflective coatings may include sublayers of many differentmaterials, some of which are as follows: Al₂O₃, ZrO₃, MgF₂, SiO₂,cryolite, LiF, ThF₄, CeF₃, PbF₂, ZnS, ZnSe, Si, Ge, Te PObTe, MgO, Y₂O₃,Sc₂O₃, SiO, HfO₂, ZrO₂, CeO₂, CeO₂, Nb₂O₃, Ta₂O₅, and TiO₂. Thesedifferent compositions are chosen by those having skill in the art tobest mate and match with the other materials used in the construction ofthe lens 1 so as to provide the transmission of light at selectedadvantageous wavelengths. Preferably, for the present invention, it isdesired to have the transmission of light be as close as possible to100% of the incident light across the entire spectrum of visible light,but especially in the center of the spectrum.

[0034] In the present invention, it is desirable to have ananti-reflective layer 18 that functions well in cooperation with thehydrophobic layer 19 to provide transmission of light through a widerange of wavelengths, especially light having a wavelength of 550 nm.Consequently, preferred for this invention are anti-reflective layer 18,sublayers 21 through 24 with sublayer 21 being adjacent to the lens face10 and with sublayer 24 being adjacent to the hydrophobic layer 19. Thepreferred composition and thickness of the sublayers is as follows:approximately 70 nm of Al₂O₃; approximately 70 nm of ZrO₃; approximately225 nm of MgF₂, and finally approximately 140 nm of SiO₂. Forembodiments of this particular invention where the AR layer and the lensare heated to between 250-300° C. before applying the hydrophobic layer,it has been found that it is important to have the final sublayer, inthis case sublayer 24, be silicon dioxide to bind with the hydrophobiclayer. Most of the other components normally utilized in anti-reflectivelayers are unsuitable for direct binding with the hydrophobic layer 19;however, it is foreseen that there may be one or more compounds otherthan silicon dioxide that may be used as the final sublayer, providedthat such a compound offers a suitable binding for the particularhydrophobic polymer used. In embodiments where the AR layer and lens arenot heated to between 250-300° C., virtually any conventional ARcompound can be adjacent the hydrophobic coating.

[0035] Prior to deposition of the hydrophobic layer 19 duringmanufacturing the lens 1 with the anti-reflective layer 18 thereon isheat-treated above ambient temperature. While different temperatures maybe utilize for different lens constructions, it has been found thatheating the lens between 250-300° C. provides a very stableanti-reflective layer 18 which is not easily removed by scratching,rubbing or normal wear. Such heat treating is not available for anydevices where the lens is constructed of plastic or of a compositematerial that does not lend itself to application of heat.

[0036] Subsequent to the anti-reflective layer 18 being applied to thelens 1, the hydrophobic layer 19 is applied. Typically, the hydrophobiclayer generally allows full transmission of light in the normal visionrange (especially at a wavelength of 550 nm) and is composed of ahydrophobic polymer. The hydrophobic layer may be applied in a layerthat is as little as several nm in thickness. The hydrophobic layer 19may be applied by dipping the lens 1 with the anti-reflective layer 18there into a liquid bath of the hydrophobic polymer which then adheresto and binds with the silicon dioxide sublayer 24, through vapordeposition or by other suitable methods. Various hydrophobic materialsmay be utilized that are well known to those skilled in the art, but areespecially chosen by those having skill in the art in conjunction withthe materials of construction of the lenses, and the anti-reflectivelayer 18 to function therewith so as to provide high light transmission.

[0037] Using another preferred method in accordance with the presentinvention, the hydrophobic coating is applied to an AR-coated lens byloading an ampule containing the hydrophobic coating into DAS Series(Denton Vacuum, Moorestown, N.J.) vacuum system. Prior to loading theampule, the DAS system was started using the System Start button and thechamber walls where heated to operating temperature (40-60° C.). Oncethe walls are at the operating temperature, the ampule was loaded intothe heater/breaker assembly and the screen above the assembly wasreplaced. The lenses were loaded into a basket in the chamber and thechamber door closed before pressing the start button. The door was heldclosed until the roughing valve opened. Once the roughing valve opened,the mechanical pump evacuated the air from the chamber and the isolationvalve opened to connect the Granville Phillips vacuum relay to thechamber. The ampule heater heated the ampule to the first set point(140-170° C.) where is was held until the vacuum set point was reached.The roughing valve remained open until the vacuum set point (5×10⁻²Torr) was reached and the LED on the Granville Phillips relay turnedgreen. Once the set point was reached, all valves closed and thedeposition process began. The ampule was heated to the secondtemperature set point (220° C.) whereupon the ampule was broken by thesolenoid. The process is stopped for two minutes at this point to allowthe chemical reaction to take place at the surface of the lenses. Whenthe top of the ampule is broken off, the liquid in the ampule hasalready been heated to vaporize and the chemical in the ampule dispersesthroughout the chamber to deposit the hydrophobic coating on the lenses.Once the deposition process is complete, the bypass valves open and thechamber is evacuated through the acid neutralization trap for twominutes. After this second pump down of the chamber, the bypass valvesclose and the isolation valve opens. The vent valve then opens to ventthe chamber to the atmosphere whereupon the end indicator light flashesand an audible alarm sounds to notify the operator that the process iscomplete.

[0038] Illustrated in FIG. 4 is a graphical representation of lighttransmission as a percentage of incoming light through a lens that hasbeen treated with a coating 15 in accordance with the present invention.As can be seen from the graph, light transmission over the range of from430-730 nm is within 1% of incident light. It is noted that thepercentage of transmission goes slightly above 100% over a small amountof the range due to expected small amounts of error intesting(signal-to-noise problems which would disappear if the data werecollected at a slower rate).

[0039]FIG. 5 illustrates light transmission through a riflescope inaccordance with the present invention in comparison to other riflescopesof similar construction but lacking the hydrophobic coating of thepresent invention. As shown in this figure, over 95% of the light at 550nm was transmitted through the riflescope. This is a great improvementover the next highest performing riflescope which permitted just over94% of the light to be transmitted through the riflescope.

[0040] Durability of a lens produced in accordance with the presentinvention exhibited superior results in both the standard eraser testand in the standard adhesive tape test. The standard eraser test wasperformed using an eraser insert complying with military specificationMIL-E-12397B. The eraser was pressure fitted into the tester beforeperforming the test. For the test, a lens having a hydrophobic coatingin accordance with the present invention was tested by pressing theeraser against the lens at a pressure of 2.5 pounds. This pressure isindicated on the indicator rod of the body of the tester containing theeraser insert. The surface of the lens was rubbed with 20 strokes of theeraser wherein each stroke was about one inch in length. All strokeswere made on one path. The lens was then washed with acetone andinspected for deterioration of the coating. No visible deterioration wasdetected after placing a drop of water on the area of the lens which hadbeen rubbed with the eraser. Further testing of the contact angles ofthe water drop would confirm that the lens with the coating retained atleast 95% of its hydrophobic characteristics after undergoing the test.Depending upon the method of applying the hydrophobic coating, thecoatings will retain between 95-100% of their hydrophobiccharacteristics after undergoing the standard eraser test. Anothermethod of testing the retention of hydrophobic characteristics as wellas durability of the coating generally includes the step of performingthe standard eraser test (as described above) and marking the lens in adirection transverse to the eraser strokes. The marking of the lens isgenerally done with a marker whereupon a strip of adhesive tape isplaced over the mark and then removed. Preferably, at least 95% of themark should be removed by the tape and the present invention exceedsthis benchmark.

[0041] A second test of durability is performed according to MIL-C-675Cand MIL-F-48616. For this test, a strip of tape approximately 1.5 inchesin length has approximately half of its length pressed onto the coatedsurface to be tested. The other half of the tape is held at an angleaway from the surface and the pressed portion of the tape is pulled upquickly. The coating of the present invention passed this test as nocoating was removed after the tape was lifted. Similarly, a second testwas performed according to MIL-M-13508. For this test, approximately oneinch of tape was placed over a portion of the coated surface such thatthe tape overlapped an edge of the object which was coated. The tape waspressed down on the coated surface as well as over the edge and thenslowly removed. The coating of the present invention also passed thistest as no coating was removed after the tape was lifted.

[0042] A third test of durability tests for crosshatch adhesion of theanti-reflective layer and the hydrophobic layer. To perform the test, alens having an anti-reflective layer and a hydrophobic layer inaccordance with the present invention was cleaned. A blade was used tomake 6 incisions towards the edge of the lens. Six additional incisionswere then made perpendicular to the first 6 incisions so that thecombination of the incisions resembled a grid pattern. The dust andparticles were removed from the grid with compressed air and the lenswas inspected to ensure that the grid contained no chips and that theincisions were even. Adhesive tape (Scotch #600, 3M) was then appliedover the cross hatch pattern with one end of the tape extending past theedge of the lens by at least ½ inches. The tape was pressed against thelens to remove any air bubbles trapped between the lens and the tape.Within 90 seconds (±30 seconds), the adhesive tape was removed byholding the lens firmly, grasping the extended end of the tape andpulling it rapidly to the other side of the lens as close to an angle of180° as possible. The entire operation was repeated two more times overa testing period of 24 hours for each of the 10 lenses tested.

[0043] Results were scored on a scale of 1 to 5 in four categories after8, 16 and 24 hours. The categories were: crazing; delamination(interlayer detachment; delamination (complete coating detachment); andcrosshatching. For the crazing assessment, lenses having no visiblecrazing received a score of A5, lenses having hairline crazing only justvisible points or cracks received a score of A4, if hairline crazingcovered up to 25% of the lens surface, a score of A3 was given, ifhairline crazing covered up to 75% of the lens surface, a score of A2was given, if hairline crazing covered the entire lens surface, a scoreof A1 was given, and if any region of the lens had severe Fern-like orMatt-like crazing, a score of A0 was given. Out of the 10 lenses tested,8 lenses received a score of A4, 1 received a score of A3, and 1received a score of A5. There were no changes in the testing over thetesting period (i.e. at 8, 16, and 24 hours).

[0044] In the interlayer delamination category, a score of B5 indicatedno delamination over the entire lens surface, B4 indicated partialdelamination of individual layers covering up to 25% of the lenssurface, B3 indicated partial delamination of individual layer coveringup to 75% of the lens surface and B2 indicated total delamination ofindividual layer over the entire lens surface. All lenses received ascore of B5 in this test over the entire testing period.

[0045] In the delamination complete coating detachment category, a scoreof C5 indicated no delamination of all layers over the entire lenssurface, C4 indicated partial delamination of all layers covering up to25% of the lens surface, C3 indicated partial delamination of all layerscovering up to 75% of the lens surface and C2 indicated totaldelamination of all layers over the entire lens surface. All lensesreceived a score of C5 in this test over the entire testing period.

[0046] Finally, in the crosshatch category, a score of D5 indicated thatthe edges of the cuts were completely smooth and none of the squares ofthe cross hatched area were detached, a score of D4 indicates that smallflakes of the coating are detached at the intersections of the squaresand the area affected is less than 5% of the total area, a score of D3indicates that small flakes of the coating are detached along the edgesand at the intersections of the squares and the area affected is between5% and 15% of the total area, a score of D2 indicates that the coatinghas flaked along the edges and on parts of the squares and the areaaffected is 5% to 15% of the total area, a score of D1 indicates thatthe coating has flaked along the edges of the cuts in large ribbons andwhole squares are detached and the area affected is 35-65% of the totalarea, a score of D0 indicates worse flaking and detachment than a scoreof D1. A lenses received a score of D5 in this test over the entiretesting period.

[0047] In summary, the coating 15 of the lens 1 is highly effective atproviding a surface coat of a hydrophobic polymer to produce beading ofmoisture on the surface of lens 1 and reduce the effect of the moisturein distorting images passing through the lens 1. The anti-reflectivelayer 18 cooperates with the hydrophobic polymer layer to providetransmission of very close to 100% of the light at the wavelengthsassociated with the normal field of vision that passes through the scope4, and therefore provides the user 6 with a very high quality image asseen through the lens 1.

[0048] It is to be understood that while certain forms of the presentinvention have been illustrated and described herein, it is not to belimited to the specific forms or arrangement of parts described andshown.

What is claimed is:
 1. A lens coating comprising: an anti-reflectivelayer comprising from about 3-7 sublayers, each of said sublayerscomprising an anti-reflective composition; and a hydrophobic layer ontop of said anti-reflective layer, said hydrophobic layer comprising anorganosilane compound, said coating retaining at least 95% of ahydrophobic characteristic after undergoing a test comprising the stepsof rubbing an eraser for at least 20 strokes along the same line using2.5 pounds of pressure on the eraser, said hydrophobic characteristicbeing selected from the group consisting of a comparison of watercontact angles before and after said test and a stain removal test usingadhesive tape.
 2. A lens and coating comprising: a lens; and a coatingdisposed on said lens, said coating comprising an anti-reflective layerand a hydrophobic layer, said anti-reflective layer comprising fromabout 3-7 sublayers, each of said sublayers comprising ananti-reflective composition, said hydrophobic layer being located on topof said anti-reflective layer and comprising an organosilane compound,said coating retaining at least 95% of a hydrophobic characteristicafter undergoing a test comprising the steps of rubbing an eraser for atleast 20 strokes along the same line using 2.5 pounds of pressure on theeraser, said hydrophobic characteristic being selected from the groupconsisting of a comparison of water contact angles before and after saidtest and a stain removal test using adhesive tape.
 3. A scopecomprising: a housing; a lens in said housing; and a coating on saidlens, said coating comprising an anti-reflective layer and a hydrophobiclayer, said anti-reflective layer comprising from about 3-7 sublayers,each of said sublayers comprising an anti-reflective composition, saidhydrophobic layer being located on top of said anti-reflective layer andcomprising an organosilane compound, said coating retaining at least 95%of a hydrophobic characterstic after undergoing a test comprising thesteps of rubbing an eraser for at least 20 strokes along the same lineusing 2.5 pounds of pressure on the eraser, said hydrophobiccharacteristic being selected from the group consisting of a comparisonof water contact angles before and after said test and a stain removaltest using adhesive tape.